Eluent Volume Research Articles

A Rapid and Simple Method for Lithium Purification and Isotopic Analysis of Geological Reference Materials by MC-ICP-MS.

A simple method has been developed to purify lithium (Li) from matrix elements in geological reference materials, using a single-column packed with AGMP-50 cation exchange resin, followed by high-precision Li isotope measurements by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). A series of tests, such as different types of resin, loading amount of Li, loading volumes, and various eluents, were conducted to ascertain the optimal conditions for Li purification and the effects of intensity, acidity, and presence of potential matrix elements on Li isotope measurements were also evaluated. In our experiment, Al and high-field-strength elements (HFSEs), such as Ti, Zr, and Hf, were eluted by 0.2 M HCl + 0.3 M HF, and 0.73 M HCl was used to separate Li from other matrix elements, such as Na. This method is suitable for processing large amount of Li (60–270 ng) and enabling a Li recovery of close to 100%, with effective removal of matrix elements such as Na and Ca. Besides, our method achieves low matrix interferences (e.g., Na/Li << 1 and Ca/Li << 1 for rock and seawater via a single-column procedure; Ca/Li < 2 for carbonate via a two-column procedure) and also uses small volume of eluents and is rapid (~5 h), enabling a total separation to be completed in ~0.5 d. Using this method, we report Li isotopic compositions of various geological reference materials, including igneous rocks, seawater, and carbonate. The Li isotopic compositions are consistent with the data published previously for the analyzed reference materials. As such, the reported method is ideally suited for Li separation from multiple types of geological samples prior to isotopic analysis.

An analytical strategy for designer benzodiazepines and Z-hypnotics determination in plasma samples using ultra-high performance liquid chromatography/tandem mass spectrometry after microextraction by packed sorbent

The illicit market for new psychoactive substances (NPS) is continuously growing. Designer benzodiazepines (DBZD) and Z-hypnotics are increasingly being used for self-medication or recreational purposes. The limited regulation and little biological information available about NPS have raised the need for analytical methods capable of extracting and quantifying them in human biological fluids. In this work, a procedure based on microextraction by packed sorbent (MEPS) in combination with ultra-high performance liquid chromatography and tandem mass spectrometry (UHPLC–MS/MS) has been developed to determine the designer benzodiazepines (clonazolam, deschloroetizolam, nifoxipam, flubromazolam and meclonazepam), and the Z-hypnotics (zolpidem, zaleplon and zopiclone) in plasma. A 3342//16 asymmetric screening design was used to study extraction variables such as the type and volume of eluent, pH, number of extraction cycles, volume of washing solvent and type of sorbent. The ensuing analytical method was validated in terms of linearity by standard addition calibration curves at eight different analyte concentration levels from 0.5–500 ng mL–1. R2 values, limits of detection (LOD) and limits of quantification (LOQ) fell in the ranges 0.9900–0.9988, 0.5–5 ng mL–1 and 1–10 ng mL–1. Intra and interday precision expressed as relative standard deviations, were < 10.6 % and process efficiency ranged from 63 to 117 % for the quality control samples. The proposed method detected zolpidem and various other benzodiazepines in plasma samples from overdoses cases.

Rapid ultrasound-assisted microextraction of atorvastatin in the sample of blood plasma by nickel metal organic modified with alumina nanoparticles.

In the present work, nickel-1,4-benzenedioxyacetic acid was synthesized as a rod-like metal organic material and then modified with alumina nanoparticles to synthesize nickel metal organic modified-Al2 O3 nanoparticles. The material was found as an efficient sorbent for the enrichment of atorvastatin in human blood plasma. After the extraction of the sample of plasma by ultrasound-assisted dispersive solid phase extraction, high performance liquid chromatography-ultraviolet was used to determine the quantitatively pre-concentrated interest analyte. The conditions for optimum extraction were achieved by the optimization of the volume of eluent, dosage of the sorbent, and time of sonication. Solution pH of 7.0, 250 μL of ethanol, 45mg of the sorbent, and 10min of sonication time were the conditions for extracting the atorvastatin maximum recovery of higher than 97.0%. By using desirability function for the optimization of the process, the present method showed a response that was linear ranging from 0.2 to 800ng/mL with regression coefficient of 0.999 in the plasma of human blood with a satisfactory detection limit of 0.05ng/mL, while the precision of interday for the current method was found to be<5%. It can be concluded that dispersive solid phase extraction method is effective for the extraction of atorvastatin from human plasma samples (97.4-102%) due to its easy operation, simplicity, repeatability, and reliability.

Determination of bongkrekic acid and isobongkrekic acid in rice noodles by HPLC-Orbitrap HRMS technology using magnetic halloysite nanotubes

The existing extraction and detection methods of bongkrekic acid (BKA) and isobongkrekic acid (IBKA) are complex, time-consuming and solvent-consuming. In this work, a simple and fast pre-concentration procedure based on Fe3O4/HNTs was developed for the determination of BKA and IBKA in rice noodles using HPLC-Orbitrap HRMS. The structure and morphology of Fe3O4/HNTs was characterized by means of XRD, SEM, FT-IR and VSM. Parameters affecting the extraction efficiency including adsorbent amount, pH, extraction time, type and volume of eluent were investigated by employing the response surface method. Results indicated that the proposed method had favorable linearity in the concentration range of 2–200 μg/L with a correlation coefficient >0.998. Method LOD and LOQ were 0.3 μg/kg and 1.0 μg/kg, respectively. Finally, the method was successfully applied to determine BKA and IBKA in rice noodle samples from southern China with recoveries ranging from 79.8% to 102.6% and relative standard deviation (RSD) of 4.2%-7.1%.

Zirconium(Ⅳ)-based metal-organic framework for determination of imidacloprid and thiamethoxam pesticides from fruits by UPLC-MS/MS

Zirconium(Ⅳ)-based metal-organic framework (MOF)-UiO-66-NH2 was fabricated to adsorb the imidacloprid and thiamethoxam in fruit samples before analysis using UPLC-MS/MS. The UiO-66-NH2 was confirmed by SEM, FTIR, and XRD. Key experimental parameters were investigated by response surface methodology (RSM). The desirability recovery of imidacloprid was 94.52% under optimum conditions (mount of adsorbent = 52.48 mg, volume of eluent = 5.18 mL, pH = 9, extraction time = 15 min). The desirability recovery of thiamethoxam was 93.57% under optimum conditions (mount of adsorbent = 50.58 mg, volume of eluent = 2.6 mL, pH = 5.65, extraction time = 11.94 min). Under the optimal conditions, the actual recovery of imidacloprid and thiamethoxam was 92.39% and 94.37%, respectively. Besides, the method was applied successfully to detect imidacloprid and thiamethoxam in different fruit samples. The results demonstrated that the UiO-66-NH2 is an excellent adsorbent for the extraction imidacloprid and thiamethoxam from fruit samples.

Magnetic molecularly imprinted polymer for the selective dispersive micro solid phase extraction of phenolphthalein in urine samples and herbal slimming capsules prior to HPLC-PDA analysis

Magnetic molecularly imprinted polymers (MMIPs)-based dispersive micro solid phase extraction (D-µ-SPE) method have many advantages, such as high selectivity, inexpensive, simplicity, facile preparation and operation, reproducibility and environmentally friendly. In this study, a new magnetic MIP based on amino functionalized Fe3O4@SiO2 nanoparticles (NPs) was synthesized. Different characterization methods including field emission scanning electron microscopy (FESEM), Fourier transform-infrared spectroscopy (FT-IR), energy dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) were applied for the characterization of synthesized MMIP. The proposed MMIPs-D-µ-SPE method was effectively utilized for the selective extraction of phenolphthalein from urine samples and herbal slimming capsules prior to HPLC-PDA analysis. Effect of different parameters, including the selection of pH of the sample, amount of MMIP, time of sorption, type of eluent, volume of eluent and time of elution, were examined and optimized. The maximum sorption capacity of the MMIP and MNIP were 138.2 and 68.5 mg g−1, respectively. The linearity was obtained over a wide concentration range of 0.05–10000 µg L-1 with coefficient of determination of 0.9996 and the detection limit (LOD) was found 0.01 µg L-1 (S/N = 3). The RSD values at three concentration levels (50, 250 and 500 µg L-1) ranged from 2.7% to 3.4% (intra-day, n = 5) and 4.5%-5.5% (inter-day) precision for three varied days. The present study proposed promising prospects of environmentally friendly MMIP based D-µ-SPE-HPLC-PDA method for highly efficient sample pretreatment and intended analytes determination in complex matrices.

Covalent organic framework Schiff base network-1-based pipette tip solid phase extraction of sulfonamides from milk and honey

In this work, a covalent organic framework Schiff base network-1 (SNW-1), was synthesized based on the Schiff base reaction between terephthalaldehyde and melamine and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and nitrogen adsorption-desorption isotherm analyses. The prepared SNW-1 was employed as pipette tip solid phase extraction adsorbent for the extraction of sulfonamides (SAs) prior to high performance liquid chromatography analysis. The parameters affecting the extraction efficiency, including the salt concentration, sample pH, amount of adsorbent, and types and volume of eluent were investigated in detail. Good linearities were obtained between the peak area and SAs concentration ranging from 5 to 500 ng mL−1 with correlation coefficients (R2) higher than 0.9998. The limits of detection and RSDs were lower than 0.25 ng mL−1 and 1.9 %, respectively. The developed method was further applied for the determination of SAs in milk and honey samples with recoveries in the range of 85.8 % – 118.0 % and RSDs less than 9.5 %. The results demonstrate that the SNW-1 shows great potential for the enrichment of trace SAs in complex matrices.

Mercury speciation in edible seaweed by liquid chromatography - Inductively coupled plasma mass spectrometry after ionic imprinted polymer-solid phase extraction

In contrast to most of essential and heavy metals, mercury levels in seaweed are very low, and pre-concentration methods are required for an adequate total mercury determination and mercury speciation in this foodstuff. An ionic imprinted polymer-based solid phase extraction (on column) pre-concentration procedure has been optimized for mercury species enrichment before liquid chromatography hyphenated with inductively coupled plasma mass spectrometry determination. The polymer has been synthesized by the precipitation polymerization method and using a ternary pre-polymerization mixture containing the template (methylmercury), a non-vinylated monomer (phenobarbital), and a vinylated monomer (methacrylic acid). Factors affecting the adsorption/desorption of Hg species (extract pH, loading and elution flow rates, volume of eluent, etc.), and parameters such as breakthrough volume and reusability, were fully studied. Mercury species were first isolated from seaweed by ultrasound assisted extraction using a 0.1% (v/v) HCl, 0.12% (w/v) l-cysteine, 0.1% (v/v) mercaptoethanol solution. Under optimized conditions, the limits of detection were 0.007 and 0.02 μg kg−1 dw for methylmercury and Hg(II), respectively. The pre-concentration factor (volume of 10 mL of seaweed extract) was 50. Repeatability and reproducibility of the method were satisfactory with relative standard deviations lower than 16%. The proposed methodology was finally applied for the selective pre-concentration and determination of methylmercury and Hg (II) in a BCR-463 certified reference material and in several edible seaweeds.

A selective and sensitive procedure for magnetic solid-phase microextraction of lead(II) on magnetic cellulose nanoparticles from environmental samples prior to its flame atomic absorption spectrometric detection

A solid-phase microextraction (SPME) procedure has been proposed for the extraction of a trace amount of lead from the environmental samples using magnetic cellulose nanoparticles (Cell-MNPs) as adsorbent material. Synthesized cell-MNPs was characterized by FTIR, SEM—EDX, XRD, and BET. Different analytical parameters were optimized such as pH, adsorbent amount, adsorption time, desorption time, eluent type, eluent volume, model solution amount, and matrix ions effects for the selective and sensitive extraction of lead (II) from the environmental samples. The limit of detection and limit of quantification were found to 8.9 and 29.7 µgL−1 for the lead (II). Cell-MNPs was successfully applied for solid-phase extraction of lead (II) from the water and tea samples.

3D printing fabrication and test of a centrifugal cartridge with an integrated gravity valve for solid phase extractions

This paper reports a truly three-dimensional centrifugal cartridge system with a novel gravity valve, multiple capillary and Coriolis switching valves. The unique design of the novel gravity valve helps to simplify the design of the fluidic system. The entire fluidic system was 3D printed, and tested for Solid Phase Extraction (SPE) enhancement applications. Other than the servo-motor used to drive the rotational movement of the system, there was no moving parts in the fluidic platform. The sequential control of these valves was simply achieved by manipulating the rotating direction and speed of the centrifugal cartridge. Anthracene, which was one of the Polycyclic Aromatic Hydrocarbons (PAHs), was used as the target analyte and tested with our design. C18 was used as the stationary sorbent and fluorescence method was adopted to detect anthracene. The concentrations of the anthracene/water testing samples were 1 μg/L (1 ppb), 5 μg/L (5 ppb), and 10 μg/L (10 ppb), respectively. The volumes of testing sample and eluent (nonane) were 10 mL and 1 mL respectively. Experiments showed that the average fluorescence intensity enhancement ratio for samples with different analyte concentrations were 11.81, 9.48, and 7.36, respectively. This centrifugal SPE system was easy to operate and could be potentially used as a portable on-site pollutant enrichment and detection device.

Spent tea leaves as an adsorbent for micro-solid-phase extraction of polycyclic aromatic hydrocarbons (PAHs) from water and food samples prior to GC-FID analysis

Spent tea leaves (STL) which is a waste from brewed tea leaves, Camellia sinensis is utilized as micro-solid phase extraction (µ-SPE) sorbent for the extraction of hazardous polycyclic aromatic hydrocarbons (PAHs) from water and food samples for the first time. STL contains lignin, cellulose, hemicellulose, polyphenols, and aliphatic carbon which enable the adsorption of PAHs. Tea filter bag is used as a porous membrane to reduce the cost. In this work, STL-µ-SPE coupled with GC-FID was successfully applied to extract 5 types of PAHs, namely fluorene, fluoranthene, pyrene, chrysene, and benzo[a]pyrene in real samples though it is challenging as PAHs usually exist in complex matrices and trace level. STL and its interaction with PAHs were then characterized by FT-IR, FESEM, and EDX analyses. The µ-SPE method was optimized by several parameters such as eluent type and volume, dosage of sorbent, extraction time, desorption time and volume of sample. Under the optimized conditions, the linear calibration curves were in the range of 50 ng mL−1 to 1000 ng mL−1 with the R2 ranged between 0.9952 and 0.9983 in the water sample. The recoveries in the real samples ranged from 88.0 to 111.4% with the RSDs (n = 3) ranged at 1.0 to 9.8%. The present method found to be fast, sensitive, cost-effective, reproducible and feasible as a new application of using low-cost adsorbent for the determination of PAHs in the water and food samples.

Determination of cobalt in food by magnetic solid-phase extraction (MSPE) preconcentration by polyaniline (PANI) and polythiophene (PTH) coated magnetic nanoparticles (MNPs) and microsample injection system – flame atomic absorption spectrometry (MIS-FAAS)

Magnetic nanoparticles (MNPs) named Fe3O4@coPANI-PTH were synthesized by coating Fe3O4 nanoparticles (NPs) with a polyaniline (PANI)/polythiophene (PTH) co-polymer. The feasibility of Fe3O4@coPANI-PTH as the nanosorbent for magnetic solid-phase extraction (MSPE) was evaluated for the determination of Co(II) in real samples using microsample injection system – flame atomic absorption spectrometry (MIS-FAAS). Parameters (sample pH, adsorbent mass, eluent volume, sample volume, and co-existing ion effects) influencing the preconcentration of cobalt were optimized. Under the optimum conditions at pH 10, cobalt was completely adsorbed by 100 mg Fe3O4@coPANI-PTH from 60 mL sample and eluted quantitatively (≥ 95%) using 1.0 mL of 0.2% thiourea solution in a mixture of 2 mol L−1 HCl and 1 mol L−1 HNO3. The adsorption capacity and characteristics of Fe3O4@coPANI-PTH for cobalt were evaluated with isotherm studies. The accuracy of the optimized method was evaluated by measuring certified reference materials (CRMs) and spiked real samples. The relative error and standard deviation were below 6.0% for the CRM and real sample analyses. The limit of detection was 1.6 μg L−1. The determination of ultra-trace cobalt amounts in various soft drinks, spice, vegetable, and water samples was achieved satisfactorily with this method.

Nano-sized Fe3O4@SiO2-molecular imprinted polymer as a sorbent for dispersive solid-phase microextraction of melatonin in the methanolic extract of Portulaca oleracea, biological, and water samples

In this study, a magnetic molecularly imprinted polymer (MMIP (Fe3O4@SiO2-MIP)) was used for the dispersive magnetic solid-phase microextraction (d-MSP-μ-E) to design an easy and effective method for melatonin (MLT) extraction in the methanolic extract of Portulaca oleracea, human urine and plasma, and water samples. HPLC with UV detection was utilized, and pH, the type and volume of eluent, MMIP mass, and contact time were considered as effective factors in the study of MLT separation and pre-concentration. These factors were optimized by Plackett–Burman and multi-objective response surface methodology (RSM). The values were 10 mg, 14 min, 4.2, methanol, 0.180 mL, 2.5 min, for the MMIP mass, time of sorption, sample pH, eluent type, eluent volume, and time of elution, respectively. At the optimum conditions, the limit of detection (LOD) was 0.046 ng mL−1, and the limit of quantification (LOQ) was 0.156 ng mL−1. The sorption capacity of the proposed MMIP sorbent was 109.1 mg g−1 at the optimum conditions. Besides, linear dynamic range (LDR) was 0.2–4200 ng mL−1, and the precision of the method (RSD %) for triplicate measurements was <6.1%. The MMIP showed saturation magnetization of 19.75 emu g−1, resulting in fast separation of the sorbent. The sorption test revealed the high sorption capacity of the MMIP for MLT and its homogeneous binding sites. In all spiked levels (50, 100, 200, and 500 ng mL−1), 93.07–104.1% was the range obtained for the recovery of MLT. The relative selectivity factor (β) values of MLT/tryptophan, MLT/serotonin, MLT/ferulic acid, MLT/mefenamic acid, MLT/quercetin, MLT/luteolin, and MLT/chlorogenic acid were 1.60, 1.68, 2.02, 2.38, 2.32, 2.40, and 2.50, respectively. The results of desorption–regeneration cycles (seven times) by employing the MMIP showed the high stability of the resultant material. In conclusion, the MMIP combined with the magnetic separation showed a specific sorption behavior for MLT and suggested a simple, flexible, selective, and powerful analytical tool.

Ultrasound-assisted magnetic solid phase microextraction of patent blue V on magnetic multiwalled carbon nanotubes prior to its spectrophotometric determination

An ultrasound-assisted magnetic solid phase microextraction procedure was developed for separation and enrichment of trace levels of patent blue V in different syrups, waters and artificial sweat samples prior to its determination by UV– Vis spectrophotometry. Three mg magnetic multiwalled carbon nanotube (mMWCNT) was used as solid phase. Several variables affecting microextraction efficiency such as sample volume, pH, matrix effect, volume and type of eluent, sample volume were investigated and optimized. The developed SPME method presents a limit of detection (LOD, N = 10) of 3,5 μgL−1, analyte recoveries were 98–100%, preconcentration factor of 250 and a relative standard deviation (RSD, %, N = 10) of 1,5% under the optimum conditions. The proposed procedure for determination of patent blue V in different environments samples is precise, accurate, very simple, practical, fast, easy to apply and economical.

In-tube stir bar sorptive extraction based on 3-aminopropyl triethoxysilane surface-modified Ce-doped ZnAl layered double hydroxide thin film for determination of nonsteroidal anti-inflammatory drugs in saliva samples

Athin-film based on 3-aminopropyl triethoxysilane surface-modified Ce-doped zinc-aluminum layered double hydroxide was synthesized on the inner surface of an aluminum tube. It has beenapplied toin-tube stir bar sorptive extraction of nonsteroidal anti-inflammatory drugs in saliva samples followed by high-performance liquid chromatography. The sorbent was characterized by scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and elemental mapping. The extraction parameters including sample pH (4.2), extraction time (10min), stirring speed (800rpm), type of eluent (acidified tetrahydrofuran), eluent volume (100μL), and desorption time (6min) were thoroughly optimized. Under the optimum conditions, limits of detection were found to be less than 5.0ngmL-1. Calibration plots were linear within the range 10-1000ngmL-1 (R2 > 0.9982). Absolute recoveries were calculated in the range 63.5 to 72.4%. The repeatability (intra- and inter-day precision) and reproducibility (tube-to-tube precision) at concentrations of 50, 250, and 500ngmL-1 were less than 7.6% and 9.4%, respectively. The method accuracy based on the relative error was calculated at these concentrations and ranged from - 4.9 to - 9.3% for intra-day relative error (%) and - 6.8 to - 11% for inter-day relative error (%). Finally, the method applicability was examined for the determination of nonsteroidal anti-inflammatory drugs in saliva samples, and good relative recoveries were obtained within the range 86.5 to 95.2%. As a result, the introduced method can be applied as a suitable alternative to measuring nonsteroidal anti-inflammatory drugs in biological fluids. Graphical abstract A surface-modified Ce-doped ZnAl LDH thin film was synthesized on the inner surface of an Al tube and applied for in-tube stir bar sorptive extraction of NSAIDs in saliva.

Magnetic dispersive micro-solid phase extraction merged with micro-sampling flame atomic absorption spectrometry using (Zn-Al LDH)-(PTh/DBSNa)-Fe3O4 nanosorbent for effective trace determination of nickel(II) and cadmium(II) in food samples

In this work, Zn-Al layered double hydroxide (Zn-Al LDH) combined with polythiophene (PTH)/sodium dodecyl benzene sulfonate (DBSNa) and Fe3O4 was synthesized and used in a centrifugeless ultrasound-assisted dispersive micro solid phase extraction (UA-D-μSPE) technique for pre-concentration and separation of Ni2+ and Cd2+ ions. The final analysis of the analytes was carried out by the micro sampling flame atomic absorption spectrometry (MS-FAAS). The influences of several effective analytical parameters, including pH value, amount of nanosorbent, sonication time, and eluent volume, on the extraction efficiency were studied by experimental design method. In the optimal conditions, the linearity ranges of 5–300 and 2.5–100 ng mL−1 for the Ni2+and Cd2+ ions were attained, respectively. The limits of detection (LODs) of the method were 1.3 and 0.7 ng mL−1 for the Ni2+ and Cd2+ ions, respectively. The proposed method demonstrated to be suitable for concurrent extraction of studied metals in various vegetable and meat samples with high accuracy and enrichment factors.

Synthesis of cellulose nanofibers functionalized by dithiooxamide for preconcentration and determination of trace amounts of Cd(II) ions in water samples

A highly efficient natural adsorbent was provided by the synthesis of modified cellulose nanofibers (CNFs) for preconcentration and determination of trace amounts of Cd(II) ions. CNFs were prepared by hydrolysis of wood pulp with strong acid under reflux and sonicating conditions and modified by immobilization of dithiooxamide. Effective factors such as pH of extraction, nanocomposite amount, extraction time, type and concentration of eluent, ionic strength, and sample volume were optimized for the quantitative determination of Cd(II) ions. Results of optimization showed a linear range between 0.1 and 10 ng ml−1 by a limit of detection of 0.04 ng ml−1. Statistical analysis showed small relative standard deviations of 2.1%, high preconcentration, and enrichment factors. The nanocomposite also showed high sensitivity and selectivity for detecting very low concentration of Cd(II) ions in real samples at ng ml−1 level with high accuracy.

Electrochemically synthesized NiFe layered double hydroxide modified Cu(OH)2 needle-shaped nanoarrays: A novel sorbent for thin-film solid phase microextraction of antifungal drugs

Herein, we applied a simple electrosynthesis process to deposit nickel-iron layered double hydroxides (NiFe LDH) on the surface of copper hydroxide (Cu(OH)2) needle-shaped nanoarrays and introduce a new sorbent for thin-film solid phase microextraction (TF-SPME). For this purpose, the nanoarrays were grown via electrochemical anodization on a copper foil’s surface and then modified with NiFe LDH. The synthesized sorbent was characterized by field emission-scanning electron microscopy, Brunauer-Emmett-Teller (BET), and Barrett-Joiner-Halenda (BJH) analysis, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The Cu(OH)2–NiFe LDH based TF-SPME method was used to measure antifungal drugs in veterinary plasma samples followed by HPLC-UV analysis. The effects of various parameters in the extraction efficiency, including pH (5.0), extraction time (20 min), stirring rate (500 rpm), and salt effect (5.0%), type of eluent (acetonitrile), eluent volume (100 μL) and desorption time (5 min) were thoroughly optimized. Under the optimum conditions, limits of detection for ketoconazole, clotrimazole, and miconazole were obtained below 10 ng mL−1. Intra-day, inter-day and film-to-film RSDs% were obtained less than 6.2%, 7.3% and 7.0%, respectively. Moreover, calibration plots were linear from 30 to 5000 ng mL−1 for ketoconazole, 8.0–1000 ng mL−1 for clotrimazole, and 15–1000 ng mL−1 for miconazole, with determination coefficients between 0.9937 and 0.9971. Finally, good relative recoveries (%) in the range of 85–97% were obtained for measuring trace amounts of antifungal drugs in dogs’ plasma samples. As a result, the method can be considered as an appropriate alternative to the conventional sample preparation methods for measuring trace amounts of antifungal drugs in biological samples.

Elecrtospun methacrylic acid‐modified polystyrene nanofiber as solid phase adsorbent for preconcentration of methyl green from aqueous samples

AbstractThis research describes the development of a new design of electrospun nanosorbent, polystyrene/methacrylic acid nanofibers (PS/MAA NFs), for the extraction and preconcentration of Methyl green (MG) from aqueous samples via solid phase extraction (SPE). The experimental parameters affecting the SPE extraction efficiency including sample flow rate through the sorbent, ionic strength and pH of the sample solution, weight of sorbent, volume and type of eluent were investigated, and optimized. Under the optimum conditions (40 ml of 1 mg/L MG, pH: 5, sample flow rate: 2 ml/min, 0.1 g PS/MAA NFs and eluting solvent: 3 ml MeOH), the calibration curve was linear in the MG concentration range of 25–1,000 μg/L. The limit of detection and enhancement factor of the proposed method, for extraction from 40 ml sample solution, were obtained as 10 μg/L and 8.3, respectively. MG dye was extracted from different real samples (urban, mineral and river waters) using the proposed adsorbent and the results showed that PS/MAA NFs were suitable for preconcentration and determination of trace amount of methyl green in wastewater samples.

Chitosan magnetic hydrogel based ligandless magnetic solid phase extraction for the accurate and sensitive determination of thallium by slotted-quartz tube flame atomic absorption spectrophotometry with matrix matching calibration strategy

In this study, a promising method was developed for the determination of thallium at trace levels by applying chitosan based magnetic solid phase extraction using slotted quartz tube atomic absorption spectrometry. Chitosan based magnetic hydrogels (CMH) were synthesized and used as solid phase extraction sorbents. The variable parameters required for the extraction method such as hydrogel amount, adsorption period and eluent volume were optimized, and under the optimized conditions, limits of detection and quantification values were recorded as 12 and 39 ng/mL, respectively. Real sample applications were performed to test the accuracy of the proposed method. For this purpose, recovery studies were carried out in two different spiking concentrations of thallium in lake water, well water and wastewater samples using the developed extraction/preconcentration method (chitosan magnetic hydrogel based ligandless magnetic solid phase extraction, CMH-LMSPE). The obtained percent recovery values of 87.2–113.2% confirmed the applicability of the method with high accuracy and precision.